SANTA CLARA -- Passing an impact test is virtually all that separates Alex Smith from playing in the 49ers' Monday night game against the Chicago Bears, eight days after he sustained his first concussion this season.

Smith officially is listed as questionable. Bears quarterback Jay Cutler has been ruled out because of a concussion, and he'll be replaced by former Raiders quarterback Jason Campbell.

On Saturday, Smith practiced for a fourth consecutive day in a black jersey, which signifies a no-contact role that is customary anyhow at practices for quarterbacks.

Offensive coordinator Greg Roman said Smith has looked sharp in practice, and when asked if Smith received the same workload as a normal week, Roman replied: "There abouts."

Smith's impact test could come in a variety of forms before Monday night's kickoff, and surely before his pregame ritual of getting slapped on the shoulder, chest and head by coach Jim Harbaugh.

When Joe Staley came off a concussion against the New York Giants, he didn't get cleared to play until he passed a contact drill in which he went against rookie linemen Joe Looney and Al Netter.

"For me, I had to bang against another person with my helmet," Staley said. "A quarterback is probably different, because his job doesn't consist of banging someone's head."

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Backup lineman Daniel Kilgore had a different final test after his Oct. 29 concussion at Arizona. After initially visiting a Stanford neurologist and laying low during the 49ers' bye week, Kilgore didn't have to bang heads with anyone before last Sunday's return against the St. Louis Rams. Instead, Kilgore said he sat down at a computer and passed a reaction-time test involving questions and lights.

In his past two "Monday Night Football" games, Smith combined to complete 36 of 50 passes (72.0 percent) with four touchdown strikes and a 123.7 rating, those coming in wins over the Pittsburgh Steelers last Dec. 19 and Arizona Cardinals on Oct. 29.

Defensive coordinator Vic Fangio doesn't expect the Bears' offensive approach to change despite their quarterback switch. "They're similar quarterbacks, strong-arm guys and athletic," Fangio said. Rather than watch film of Campbell from his Raiders tenure the past two seasons, the 49ers have studied his action in the exhibition season and last Sunday's second half against Houston.

Roman was pleased with backup quarterback Colin Kaepernick's "off the cuff" plays he made in relief of Smith in Sunday's 24-24 tie with the St. Louis Rams. "Kap's a guy that's improving all the time," Roman said.

The 49ers have had trouble this season covering slot receivers or short, quick targets out of the backfield. That includes the Green Bay Packers' Randall Cobb, the Minnesota Vikings' Percy Harvin, the New York Giants' Victor Cruz and the St. Louis Rams' Danny Amendola. Could the Bears' Devin Hester be next in that line?

"The guys you're alluding to, everyone has had a hard time covering," Fangio said. "We've gone against good slot receivers and they've caught balls on us, but I don't see it as an epidemic." The 49ers have not considered replacing Carlos Rogers with Perrish Cox as their slot-cover guy, Fangio added.